Stats Exam 2 - Chapters 9-11

a) True

Paired-samples t tests are particularly well suited to research studies that examine learning or other changes that occur over time. a) True b) False

d) too small to be of interest.

Researchers examined the impact of candy on students' test performance and found that candy significantly increased test performance. When they examined the effect size, they found that Cohen's d was .02. Based on convention this is considered: a) small. b) medium. c) large. d) too small to be of interest.

d) differences between means.

The comparison distribution for an independent-samples t test is a distribution of: a) means. b) scores. c) mean difference scores. d) differences between means.

a) order effects.

The fact that a research participant encounters the dependent variable twice in a within-groups design means that we have to be concerned about: a) order effects. b) using statistics. c) compensating participants. d) gender differences.

b) pooled variance.

The weighted average of the two estimates of variance (one from each sample) that are calculated when conducting an independent-samples t test is referred to as: a) standard error. b) pooled variance. c) degrees of freedom. d) the confidence interval.

c) Cohen's d.

To calculate effect size for a paired-samples t test we use: a) eta squared. b) the p statistic. c) Cohen's d. d) the z statistic.

b) if the sample size is big and the sample variance is small

Under what circumstances can a very small treatment effect be statistically significant? a) if the sample size is big and the sample variance is also big b) if the sample size is big and the sample variance is small c) if the sample size is small and the sample variance is big d) if the sample size and the sample standard deviation are both small

b) The t test uses the estimated standard error while the z statistic uses the actual standard error of the population of means.

What is the difference between the z and t tests? a) The z test uses the estimated standard error while the t statistic uses the actual standard error of the population of means. b) The t test uses the estimated standard error while the z statistic uses the actual standard error of the population of means. c) The z test uses the estimated standard deviation while the t statistic uses the actual standard deviation. d) The t test uses the estimated standard deviation while the z statistic uses the actual standard deviation.

b) It is flatter and more spread out than the normal distribution.

When N is small (less than 30), how does the shape of the t distribution compare to the normal distribution? a) It is almost perfectly normal. b) It is flatter and more spread out than the normal distribution. c) It is taller and narrower than the normal distribution. d) There is no consistent relationships between the t distribution and the normal distribution.

d) independent-samples t test.

When conducting a study of gender differences, we have to employ a(n): a) single-sample t test. b) paired-samples t test. c) dependent-samples t test. d) independent-samples t test.

b) False

When determining the critical value for an independent-samples t test, you use the degrees of freedom for the smaller sample. a) True b) False

a) distribution of differences between means.

When using an independent-samples t test, we have to create a: a) distribution of differences between means. b) difference score for each participant. c) distribution of differences between raw scores. d) distribution of mean differences.

b) We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample.

Why is it necessary to use the pooled variance when conducting an independent-samples t test? a) Using the pooled variance helps the researcher identify skewness. b) We are working with two samples and an estimate of spread based on two samples is likely to be more accurate than an estimate of spread based on a single sample. c) It is necessary to estimate the standard deviation of the two samples in order to compare the two samples to one another. d) Estimating the spread of the sample using the standard deviation increases the generalizability of results.

b) They would decrease (move closer to zero).

With α = .05 and df = 8, the critical values for a two-tailed test are t = ± 2.306. Assuming that all other factors are held constant, if the df value were increased to df = 20, what would happen to the critical values for t? a) They would increase (move farther from zero). b) They would decrease (move closer to zero). c) They would stay the same. d) There is not enough information provided to answer this question.

c) dependent-samples t test.

A paired-samples t test is also known as a(n): a) single-sample t test. b) independent-samples t test. c) dependent-samples t test. d) confidence interval.

a) single-sample t test

A(n) _____ is a type of t test in which we compare data from one sample to a population for which we know the mean but not the standard deviation. a) single-sample t test b) nonparametric t test c) independent-samples t test d) dependent-samples t test

b) A between-groups design

An independent-samples t test is used with which type of research design? a) A within-groups design b) A between-groups design c) A paired-samples design d) A single-sample design

b) gets progressively wider.

As sample size decreases, the shape of the t distribution: a) gets progressively narrower. b) gets progressively wider. c) more closely matches the z distribution. d) is more accurate.

c) dependent procedures reduce the variability in the sampling distribution. *Dependent vs. independent -independent - different subjects -dependent - within groups - same subjects are in both groups

Dependent sampling generally results in a more powerful statistical test than independent sampling because: a) the dependent procedure generally has a larger N. b) dependent procedures have higher acceptable levels of a c) dependent procedures reduce the variability in the sampling distribution. d) All of these are correct.

b) 43.27 to 50.73

For a paired-samples t test, Mdifference = 47 and sD = 7, N = 16, the 95% confidence interval is: a) 32.08 to 61.92 b) 43.27 to 50.73 c) 43.15 to 50.85 d) none of the above **SEE EQUATION

a) 2

For a repeated-measures study comparing two treatments, a researcher obtains a sample of N = 9 difference scores with a Mdifference = 4 and a variance of s2 = 36. What is the value for the tparied statistic for these data? a) 2 b) .67 c) .33 d) .11 **SEE EQUATION

a) True

If a hypothesis test using a sample of n = 15 scores produces a t statistic of t = 2.15, then the correct decision is to reject the null hypothesis for a two-tailed test with an a of 0.05. a) True b) False

a) fail to reject the null hypothesis

If a t score is calculated to be -.03 and our critical values are -2.365 and 2.365, what decision do we make about our research study? a) fail to reject the null hypothesis b) reject the null hypothesis c) accept the null hypothesis d) accept the research hypothesis

a) True

In a repeated-measures study, a small variance for the difference scores indicates that the treatment effect is consistent across participants. a) True b) False

b) False

In general, the larger the value of the sample variance, the greater the likelihood of rejecting the null hypothesis. a) True b) False

a) research hypothesis.

It is hypothesized that there is a significant difference in depression levels between men and woman in a college dormitory. This hypothesis best illustrates a: a) research hypothesis. b) null hypothesis. c) standardized hypothesis. d) directional hypothesis.

d) a paired-samples t test

It is hypothesized that there will be a significant difference in aggression scores after caffeine consumption as compared to before caffeine consumption. This hypothesis best illustrates what type of t test? a) a single-sample t test b) a nonparametric t test c) an independent-samples t test d) a paired-samples t test